In a conventional hydraulic brake system, front to rear brake proportioning is typically fixed by the hydraulic design of the brakes and proportioning valves in the brake system.
More recently, there have been proposals for various drive-by-wire brake systems in which front to rear proportioning need not be fixed by system hydraulics and can be controlled instead by an electronic controller operating on one or more brake actuators. Such systems allow dynamic front to rear brake proportioning, that is, brake proportioning that is not fixed, but can be adjusted during vehicle driving and/or braking to achieve a desired result.